Process for making biodegradable detergents



United States Patent f 3,355,484 PROCESS FOR MAKING BIODEGRADABLEDETERGENTS Herman S. Bloch, Skokie, 11L, assignor to Universal OilProducts Company, Des Plaines, 111., a corporation of Delaware NoDrawing. Filed Aug. 20, 1964, Ser. No. 390,996 6 Claims. (Cl. 260505)This invention relates to a process for the production of detergents andother surface active agents containing a hydrophobic alkylaryl radicalwhich is subject to bacterial attack during sewage treatment. Morespecifically, this invention relates to a process for the production ofsurfactant product consisting of substantially straightchain,alkyl-substituted aromatic compounds formed by condensing butadiene withan alkylbenzene containing an alphahydrogen group in the presence of analkaline catalyst, thereby promoting side-chain telomerization,hydrogenating the unsaturated product under selective catalyticconditions to form the phenyl alkanes by side-chain hydrogenation, andintroducing a hydrophilic radical into said phenyl alkane, as forexample, by sulfonation. The resulting product which contains both ahydrophobic and a hydrophilic group is a detergent product subject tobacterial attack and degradation in a subsequent sewage treatmentprocess after the detergent has been used in a laundering or othercleaning operation and discharged ultimately into such sewage treatmentfacilities.

One of the major problems prevalent in centers of population throughoutthe world is the disposal of sewage and the inactivation of detergentsdissolved in the sewage in even small quantities. Such disposal problemis especially vexacious in the case of those detergents having analkylaryl structure as the nuclear portion of the detergent molecule.These detergents produce stable foams in hard or soft water in suchlarge quantities that the foam clogs sewage treatment facilities andoften appears in suflicient concentration in such facilities to destroythe bacteria necessary for sufiicient biological action for propersewage treatment. One of the principal offenders of this type ofdetergent is the alkylaryl sulfonates, which, unlike the fatty acidsoaps, do not precipitate when mixed with hard water containing calciumor magnesium ions in solution. Since these compounds are only partlybiodegradable, the detergent persists in solution and is carried throughthe sewage treatment plant in substantially unchanged or stillactive-form. Having an abiding tendency to foam, especially when mixedwith aerating devices and stirrers, the material causes large quantitiesof foam to be discharged from the sewage digestion plant into rivers andstreams where the continuing presence of the detergent is marked bylarge billows of foam on the surface. Other offenders of this type ofdetergent are the polyoxyalkylated alkylphenols and the polyoxyalkylatedalkylanilines. These same synthetic detergents also interfere with theaerobic process of degradation of other materials such as grease andthus compound further the pollution caused by sewage plant efiluentscontaining such detergents. These dilute detergent solutions often entersub-surface water currents which feed into underground water strata fromwhich many cities draw their water supplies and the alkylaryl-baseddetergents find their way into the water supplies drawn from water tapsin homes, factories, hospitals and schools. Occasionally, thesedetergents turn up in suflicient quantities in tap water to makedrinking water foam as it pours from the tap.

Although the eflluents from cities sewage plants may be clear and appearnon-contaminated, many tons of synthetic detergents which have resistedthe sewage treatment and which have survived the bacterial actionnormally present in open surface streams cause the formation PatentedNov. 28, 1967 of large masses of foam at the bottom of weirs and dams inwater streams fed by sewage plant efiiuents from cities whosepopulations utilize large quantities of synthetic detergents. During1959 over 1.5 billion pounds of surface active agents (on the unbuiltbasis, exclusive of the inorganic salts added to commercial detergents)were sold in the United States. Of this quantity of synthetic detergentsentering the sewage treatment facilities throughout the United States,it is estimated that 530 million pounds were of the bacterially,incompletely degradable (hard), synthetic alkylbenzene sodium sulfonatetype.

An adequate supply of pure water, like clean air, is essential to thefurther growth and development of cities and the maintenance of humanhealth standards. It has been found that alkylaryl-based detergents,such as the sodium sulfonate derivatives of these alkylarylhydrocarbons, phenols, and amines, are more readily degradable by sewagebacteria if the long-chain alkyl substituent on the phenyl nucleus is ofa simple, straight-chain configuration than if it is of a more complexbranched-chain structure. As an example, detergent compounds containingan alkylaryl hydrophobic group in which the alkyl side-chain has astructure such as the following:

are more likely to be bacterially digested than detergents of the samechemical composition but in which the alkyl radical is a more highlybranched-chain isomeric structure such as:

Thus, alkylaryl-based detergents in which the alkyl portion of themolecule has a relatively straight-chain structure, such as the alkylgroup illustrated in the first of the two structures above, producebiologically soft detergents which readily undergo bacterial degradationin the treatment of sewage and do not appear as active detergents in theeflluents of such sewage treatment plants.

It is an object of this invention to produce a detergent containing analkylaryl group in which the alkyl sidechain attached to the aromaticnucleus has a relatively straight-chain structure capable of biologicaldegradation during the treatment of sewage containing such detergents.Another object of this invention is to provide a method of attaching asubstantially straight-chain alkyl group onto an aromatic nucleus toproduce a structure suitable for the production of biologically softdetergents. It is another object of this invention to provide a methodof forming a substantially straight-chain alkyl group and simultaneouslyattaching said straight-chain alkyl group to an aromatic nucleus toproduce a structure suitable for the production of biologically softdetergents and without sacrifice of its water solubility.

In one of its embodiments this invention relates to a process for theproduction of detergents which comprises the steps: condensing butadienewith an alkylbenzene containing an alpha-hydrogen group in the presenceof an alkaline catalyst at elevated pressure and temperature,hydrogenating the alkyl side-chain of the condensed product in thepresence of a selective hydrogenation catalyst at elevated pressure andtemperature to produce the, phenyl alkane, and introducing a hydrophilicgroup into said phenyl alkane.

In another of its embodiments this invention relates to the step ofcondensing butadiene with an alkylbenzene containing an alpha-hydrogengroup in the presence of an alkaline catalyst to produce the followingcompound:

wherein R and R are independently selected from the group consisting ofhydrogen, methyl, ethyl, propyl or butyl, and n is a number from 1 to 4.

The heart of this invention lies in the forming of the straight-chainalkyl group by the telomerization of butadiene with an alkylbenzenecontaining an alpha-hydrogen where R and R are independently selectedfrom the group consisting of hydrogen, methyl, ethyl, propyl and butyland n is a number from 1 to 4. It is preferable that R and R both not behydrogen as the resulting l-phenyl alkane yields sulfonates of poorwater solubility. The alkylbenzene is preferably selected from the groupconsisting of toluene, ethylbenzene, n-propyl benzene, cumene,secbutylbenzene, sec-amylbenzene and sec-hexylbenzene. Especiallypreferable alkylbenzenes are ethylbenzene and n-propylbenzene since theywould yield 2-phenyl and S-phenyl alkanes, respectively, which willprovide phenyl alkane sulfonates of good water solubility anddetergency.

The alkylbenzene and the reaction operating conditions shouldbe.selected. such that the finally produced. phenyl alkanes contain a totalnumber of. carbon atoms of from about 15 to about 2.4 and preferablyfrom about, 16 to about 22. carbon atoms per molecule. The reactoroperating conditions should be selected to. avoid polymerization of thebutadiene or the formation of undesirable side products. The primaryoperating variables are pressure, temperature, liquid hourly spacevelocity (LHSV, volumes of feed per hour per volume of catalyst) andmole ratio of alkylbenzene. to to butadiene- Typical operatingconditions are temperature ranges of from about 80 to about 200 C.,pressures of ham about 200, to about 2,Q00. p.s.i.a.,. LHSV of fromabout 0.5 to about 5.0 and alkylbenzene to butadiene mole ratios of atleast 1.5 to. 1 and higher. The operating conditions are selected notonly to obtain a highly selective reaction but also to obtain highyields and to economically produce the condensed product. The.unconverted alkylbenzene and condensed product having less than 16carbon atoms, per molecule may be recycled back to the reaction zone toincrease the ultimate yield, while the desired product is sent to the.second step of the process.

The condensation reactionv may be typicallycarried-out by loading thealkaline catalyst. into a fixed bed reactor and pressuring up tooperating conditions with nitrogen. The temperature may be maintained bypreheating the feed streams or by heaters on the reactor. The. liquidfeed alkylbenzene. and butadiene are pumped into the reactor along withnitrogen whereupon the condensation reaction occurs. The reactoreffiuent is withdrawn and is thereafter separated into a gas phasecomprising nitrogen and small amounts of unconverted butadiene, whichare recycled back to the reactor, and a liquid phase comprisingcondensed product having the desired number of carbon atoms. permolecule, unconverted alkylbenzene and condensed product having too fewcarbon atoms per molecule. The unconverted alkylbenzene and condensedproduct having too few carbon atoms are separated. from the desiredcondensed product by ordinary fractionation and recycled back to the:reactor. Additional makeup' nitrogen may be provided to compensate forlosses of dissolved gas in the liquid phase. 7

The second major step in this process is the selective hydrogenation ofthe aliphatic side-chain as shown by the following reaction:

wherein R, R and n are as described hereinbefore. The hydrogenation ofthe aryl portion of the molecule is avoided byselection of appropriatehydrogenation conditions and a suitable hydrogenation catalyst. Apreferable catalyst is a copper chromite catalyst comprising chromiumoxide and copper oxide upon a high surface support. Typicaloperatingconditions are temperature ranges of from'abou-t 50 to about 300 C. andpressure ranges of from about 25 to about 1,000 p.s.i.a. Other selectivecatalysts which maybe used are Group VIII metals, particularly nickeland palladium; These selectively hydrogenate olefinic unsaturation attemperatures somewhat lower than required for copper-chromite, roomtemperature being sometimes sufficient for hydrogenation with nickelsupported on kiesclguhr. The condensed" product is introduced into afixed bed containingthe above-described hydrogenation catalyst in thepresence of excess hydrogen and the reactor efiuent is withdrawn fromthe reactor bed. The unconverted hydrogenis separated as a gas phase andis recycled back to the hydrogenation reactor bed while the desiredhydrogenated phenyl' alkane product is withdrawn from the system.

The hydrophobic phenyl alkane is converted into a detergent by theintroduction ofa hydrophilic group into the molecule. This is readilyaccomplished by sulfonation. The phenyl alkane may be typicallysulfonated by mixing with an equal volume of liquefied n-butane and thenwith 30% oleum which isadded to the dilute phenyl alkane mixture as asmall stream flowing onto the chilled surface of a rotating cylinder,the surface of the cylinder beingcooled bycirculating salt water at *(3C. on the inside of the cylinder as the latter is rotated. Thesuifonationmixture is' scraped from the surface of the cylinder and themixture re-spread on the cylinder by a stainless steel blade, then-butane evaporated into a hood as the heat of reaction raises thetemperature and boils off the butane, thereby maintaining thetemperature ator near the boiling point of n-butane at about 0 C. Thesulfonated reaction mixture removed from the rotating cylinder isdiluted by mixing with ice water. The resulting sulfonic and sulfuricacids dissolved in the aqueous solution are neutralized to a pH of Iwith sodium hydroxide. The product, is a crystalline, white solid whichis completely soluble in water. The evaporated solids are extracted with70% ethanol and the ethanol extract is evaporated to dryness to recoversodium sulfate-free products. The product is thereafter mixed withsufiicient sodium sulfate, sodium tripolyphosphate and other buildersalts to provide detergent compositions containing about a /80 weightratio of sodium alkylaryl sulfonate to builders.

Example I A catalyst comprising 20% potassium amide on lithiated alumina(0.5% Li as Li O) is loaded into a block type isothermal fixed bedreactor. Special precautions are taken to avoid the introduction ofmoisture into the catalyst bed. Toluene and butadiene are introducedinto the catalyst bed continuously at a 2 LHSV and at a toluene tobutadiene mole ratio of 3211.0. The reactor is maintained at 800 p.s.i.and at a 140 C. inlet catalyst bed temperature, resulting in a catalystpeak temperature of 155 C. The toluene-free product contains thefollowing aromatics:

Weight percent C H CH (CH CH=CH-CH )H 20.6 C H CH (CH CH=CHCH H 55.7 C HCH (CH CH CHCH H 14.7 C5H5CH2 4H 8 .9

Example II A condensed product is prepared by the method described inExample I, although ethyl benzene is used instead of toluene. Thecondensed product is separated into a fraction in the C to C range. Saidfraction is hydrogenated over a copper oxide-chromium oxide catalyst at125 C. to yield the G -C phenyl alkane. The phenyl alkane is sulfonatedas hereinbefore described to produce a water-soluble detergent.

A second sample of detergent is prepared by alkylating benzene with aso-called propylene tetramer which consists of a mixture of isomers andhomologs, all of which are of highly branched-chain structure containingdimethyl groupings as well as methyl and other short side-chains on themain carbon skeleton. The alkylate is sulfonated as hereinabovedescribed to produce a highly branched detergent. Samples of each of theabove detergent preparations are separately subjected to simulatedsewage treatment conditions in order to determine the relative rates ofremoval and the extent of disappearance of each of the samples from asynthetic sewage mixture of known composition. A 0.003% aqueous solutionof each of the above detergents (100 gallons each) is prepared and toeach of the solutions are added 0.5 pounds of urea (to supply nitrogennutrient), 0.2 pounds of sodium sulfate (to supply 80.; nutrient) andtrace quantities of zinc, iron, magnesium, manganese, copper, calciumand cobalt to provide the necessary nutritional requirements of thebacteria. The latter bacteria were supplied in the form of a one-poundcake of activated sewage sludge recovered from a sewage treatment plant.The simulated sewage composition, placed in a large circular tank, isstirred as air is introduced through fritted glass nozzles into thebottom of the tank in the form of fine bubbles. Approximately 50 cc.samples of the sewage suspension are removed from each of the tanks atthree-hour intervals after an initial digestion period of 24 hours,filtered, and equal quantities of the filtrate (50 cc.) measured intoshaker bottles to determine the height of foam produced after shakingeach of the samples of filtrate under similar test conditions. Typicalresults of foam height determination, which is an empirical measure ofthe amount of detergent remaining in solution, are presented in thefollowing Table I for a branched-chain alkyl group such as that preparedby alkylation of propylene tetramer and for a straight-chain alkyl groupsuch as that prepared by the process of this invention.

TABLE I.HEIGHT OF FOAM PRODUCED FROM 50 CC. SAMPLES OF SEWAGE SOLUTIONASA FUNCTION OF TIME Foam Height, cm. Time Treatment Sample in HoursBranched-Chain Straight-Chain Alkyl Group Alkyl Group DetergentDetergent I claim as my invention:

1. A process for the production of detergents which comprisestelomerizing butadiene with an alkylbenzene containing an alpha-hydrogengroup and from 1 to 8 carbon atoms in the alkyl group in the presence ofalkaline catalyst selected from the group consisting of alkali metal,alkali metal amide, alkali metal oxide, alkali metal alkoxide and alkalimetal hydride dispersed on a refractory oxide support at a temperatureof from about to about 200 C., pressure of from about 200 to about 2,000p.s.i.a., LHSV of from about 0.5 to about 5.0 and alkylbenzene tobutadiene mole ratio of at least 1.5 to 1 to linearly add the butadieneto said alkyl group, hydrogenating the aliphatic side-chain of theresultant telomerization product with hydrogen at a temperature of fromabout 50 to about 300 C. and a pressure of from about 25 to about 1000p.s.i.a. in the presence of a hydrogenation catalyst selected from thegroup consisting of Group VIII metals and copper chromite to form phenylalkane, and introducing a hydrophilic sulfonic acid group into saidphenyl alkane.

2. The process of claim 1 further characterized in that the alkalinecatalyst comprises potassium amide on lithiated alumina.

3. The process of claim 1 further characterized in that the hydrophilicgroup is introduced into the phenyl alkane by sulfonation producing thesulfonic acid derivative and neutralized with a salt-forming base toproduce a watersoluble aryl-aryl sulfonate detergent.

4. The process of claim 1 further characterized in that thehydrogenation catalyst comprises copper chromite dispersed on a highsurface support.

5. The process of claim 1 further characterized in that saidalkylbenzene is selected from the group consisting of toluene,ethylbenzene, n-propylbenzene, cumene, secbutylbenzene, sec-amylbenzeneand sec-hexylbenzene.

6. The process of claim 1 further characterized in that saidalkylbenzene is ethylbenzene and said alkaline catalyst comprisespotassium amide on lithiated alumina.

References Cited UNITED STATES PATENTS 2,984,691 5/ 1961 Fotis 260-5053,128,318 4/1964 Meisinger et al 260688 3,154,595 10/ 1964 Donaldson260-671 3,196,174 7/ 1965 Cohen 260505 3,206,519 9/1965 Eberhardt 260671LORRAINE A. WEINBERGER, Primary Examiner.

R. K. JACKSON, Examiner.

M. WEBSTER, Assistant Examiner.

1. A PROCESS FOR THE PRODUCTION OF DETERGENTS WHICH COMPRISESTELOMERIZING BUTADIENE WITH AN ALKYLBENZENE CONTAINING AN ALPHA-HYDROGENGROUP AND FROM 1 TO 8 CARBON ATOMS IN THE ALKYL GROUP IN THE PRESENCE OFALKALINE CATALYST SELECTED FROM THE GROUP CONSISTING OF ALKALI METAL,ALKALI METAL AMIDE, ALKALI METAL OXIDE, ALKALI METAL ALKOXIDE AND ALKALIMETAL HYDRIDE DISPERSED ON A REFRACTORY OXIDE SUPPORT AT A TEMPERATUREOFFROM ABOUT 80* TO ABOUT 200* C., PRESSURE OF FROM ABOUT 200 TO ABOUT2,000 P.S.I.A., LHSV OF FROM ABOUT 0.5 TO ABOUT 5.0 AND ALKYLBENZENE TOBUTADIENE MOLE RATIO OF AT LEAST 1.5 TO 1 TO LINEARLY ADD THE BUTADIENETO SAID ALKYL GROUP, HYDROGENATING THE ALIPHATIC SIDE-CHAIN OF THERESULTANT TELOMERIZATION PRODUCT WITH HYDROGEN AT A TEMPERATURE OF FROMABOUT 50* TO ABOUT 300* C. AND A PRESSURE OF FROM ABOUT 2K TO ABOUT 1000P.S.I.A. IN THE PRESENCE OF A HYDROGENATION CATALYST SELECTED FROM THEGROUP CONSISTING OF GROUP VIII METALS AND COPPER CHROMITE TO FORM PHENYLALKANE, AND INTRODUCING A HYDROPHILIC SULFONIC ACID GROUP INTO SAIDPHENYL ALKANE.